This invention is related to a sealing means for an internal combustion engine, and in particular to an improved sealing means for the combustion cylinder of such an engine.
A wide variety of head gaskets and fire rings are known. However, there remains a problem of effective sealing, especially where an engine from time to time fails to receive uniformly the requisite coolant. In such instances a so-called "thermal push" may occur, i.e., an improperly cooled zone of the engine, such as the head, will "grow" as a result of overheating, and will then excessively compress the sealing means, such as a fire ring. Usually the gasket will seal effectively under excessive compressive loads. However when the engine cools down, the opposite of thermal push occurs and the sealing effect of the gasket in the excessively compressed areas will be lost. Upon reuse of the engine, the area which has been excessively compressed will not seal until that area again becomes overheated. Sometimes the specific area may not become overheated in the same way. In either instance, the gasket will not properly seal and this may result in a significant loss of compression and power, and sometimes can result in damage to, or destruction of, the engine itself.
Various approaches to solving the problem have been attempted. Thus, strategically located metal shims have been used. However that requires adjuncts and does not guarantee that they will always necessarily be located where a thermal push may possibly occur. Another solution has been the use of a metallic plate head gasket with embossments around the combusion openings. Metallic plates, however, bring with them other problems of sealing, including the necessity for adjuncts, such as grommets and the like, around coolant openings and the like.
Still another suggested solution would be the use of embossed ring in place of a typical armored fire ring. Such a ring could employ a typically embossed metallic annulus, either with conventional embossing (as illustrated in U.S. Pat. No. 4,312,512), or with shear embossing. The size and shape of the bead on one side and the recess on the other, are typically about the same in prior art embossments. Neither of these effectively and efficiently solve the thermal push problem.
It would be desirable to be able to use more conventional laminated head gaskets using fiber-elastomer facings, and of the general type illustrated in Ascencio U.S. Pat. No. 3,565,449, and to provide fire rings for use therewith which accomodate to and solve the thermal push problem.